There are several medical conditions which currently require surgery and/or the use of an abdominal aortic graft. These conditions include: abdominal aortic aneurysms, aortic and iliac occlusive disease following balloon angioplasty and aorta-distal arterial embolization. Each of these conditions most commonly affects the aorta immediately below the take off or junction with the renal arteries through and including the area where the aorta divides into the common iliac arteries.
For illustrative purposes, consider a patient having an abdominal aortic aneurysm. An aneurysm is defined as a sac formed by localized dilatation of the aorta. Aneurysms can lead to occlusion and more notably rupture of the arterial wall and thus unconfined bleeding into the abdomen. If left untreated, the patient may die of internal bleeding.
One method of treating this disorder is through the use of an arterial replacement. However, even though the mortality rate for elective aneurysm resection is usually less than 5%, the morbidity of the needed surgery is quite severe. The average hospital stay is ten to fourteen days at a total cost of tens of thousands of dollars. For ruptured aneurysms, the hospital mortality rate is approximately 75% with greater than 2/3 of the deaths occurring during surgery or within a few hours after surgery. For survivors, the morbidity includes limb and bowel loss and renal failure requiring life long dialysis. When an aortic aneurysm ruptures, resource consumption rises astronomically. There are also a great number of patients in whom co-morbid factors constitute relative or absolute contraindications to this type of surgery such as patients with severe coronary artery disease or pulmonary insufficiency.
Another technique involves the insertion of a graft of material within the existing aorta and anchoring the graft in place such that it acts to carry blood through the afflicted portion of the aorta. This is analogous to fixing a leaking pipe by placing another pipe of smaller diameter within the existing pipe and, in essence, bypassing the afflicted area of the aorta. However, the technique does have some problems, including difficulty in accurately sizing and delivering the graft in a bifurcated blood vessel. One problem, for example, is that until surgery begins, it is often difficult to know exactly the length of a graft which will actually be required to reach from the affected area of the aorta just below the renal arteries down to and through the iliac arteries. While surgeons can estimate the necessary length, a graft which is too long may buckle or kink once flow is restored. If, on the other hand, the graft is too short then when a stent is released to anchor the graft in place, it may expand in an already weakened portion of the aortic or iliac arteries and cause rupture, leakage or other complications.
Perhaps the biggest problem, however, is getting both of the lower or iliac ends of the graft, which are to be disposed in the right and left iliac arteries, properly aligned and positioned while, at the same time, controlling the placement of the upper or aortic end of the graft. While a number of techniques have been suggested, the most common techniques use two guide wires which are inserted through the common femoral artery of one leg up into the body. A first guide wire is inserted through the common femoral artery in one leg such that its free end dangles in the aorta around the junction with the renal arteries. The other guide wire is fed in through the same leg and crosses over from one iliac artery into the other iliac artery and out through an incision in the common femoral artery of the other leg. See, for example, FIGS. 9 through 12, and the accompanying text of Baron et al., U.S. Pat. No. 5,360,443. The loose guide wire is used to guide the entire stent and graft assembly into the abdominal aorta above the iliac divide. The aortic or proximal end of the graft is exclusively fed through the femoral artery with the two iliac ends of the graft trailing behind. Thereafter, the second guide wire, which is looped up through both iliac ends of the graft, is used to help try to position the crossover iliac end into proper position in the iliac artery of the other leg. Beside the obvious difficulties in maneuvering the device, it is difficult to ensure that the graft does not become twisted and blocked during deployment. It is also difficult to control the placement of, in particular, the iliac portion of the graft which is being maneuvered into the non-insertion iliac artery.
Baron et al. also discloses insertion of an apparatus intraluminally to the aorta and in particular, to a ruptured aneurysm, through the axillary artery in the patients arm. See, for example FIGS. 13 and 14. However, this method and device appear limited to use in connection with ruptured aneurysms and Baron, et al. does not disclose the ability to accommodate a bifurcated graft.
Palmaz, et al., U.S. Pat. No. 5,316,022 disclosing inserting two individual grafts, rather than one bifurcated graft, through the individual femoral and iliac arteries up into the aorta. This leads to uniform sacrifice of the internal iliac circulation and would only be feasible in patients in whom both internal iliac arteries are already occluded. Also, the proximal end of the double individual graft stents will not, in all likelihood, produce a complete seal.